1. Field of the Invention
The present invention relates to a vane pump and a vapor leakage check system having the vane pump.
2. Description of Related Art
JP-A-2009-138602 describes a vane pump having a rotor and a motor. When the rotor is rotated by the motor, fluid is compressed, and the compressed fluid is discharged from the vane pump. The vane pump is used for decompressing or compressing an inside of a fuel tank in an vapor leakage check system that checks a leakage of vapor fuel from the fuel tank.
The rotor has an approximately cylindrical column shape, and is arranged in a pump chamber. The pump chamber has an inlet port connected to an orifice and a canister, and an outlet port connected to outside atmospheric air. The inlet port and the outlet port are located on the same end of the pump chamber in an axis direction.
However, a pressure difference is generated between the end of the pump chamber having the inlet port and the outlet port and the other end of the pump chamber in the axis direction. In this case, a pressure gradient is generated in the axis direction, thereby affecting a posture of the rotor. If the pressure gradient causes an unstable rotation of the rotor, a pumping property of the vane pump may become unstable.